We report the first experimental observation of bright EPR beams produced by a type-II optical parametric oscillator operating above threshold at frequency degeneracy. The degenerate operation is obtained by introducing a birefringent plate inside the cavity resulting in phase locking. After filtering the pump noise, which plays a critical role, continuous-variable EPR correlations between the orthogonally polarized signal and idler beams are demonstrated.
@article{arxiv.0804.0508,
title = {Experimental demonstration of frequency-degenerate bright EPR beams with a self-phase-locked optical parametric oscillator},
author = {Gaelle Keller and Virginia D'Auria and Nicolas Treps and Thomas Coudreau and Julien Laurat and Claude Fabre},
journal= {arXiv preprint arXiv:0804.0508},
year = {2008}
}